Its in the markup help just above the message body on the posting screen.
Quote:
You may also deliberately name links by using the following syntax: [ link = http ://URL GOES HERE]TITLE of link goes here[/link ]
But leave out the spaces!
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9. ..... You may not buy, sell or auction (or host or facilitate the ability to allow others to buy, sell or auction)any Game characters, items, coin or copyrighted material.